It is well-known in the prior art that liquids may be atomized by vibrating a nozzle often referred to as an acoustic horn. Such nozzles are often vibrated in their longitudinal direction by piezoelectric crystals in response to electrical signals in the 60 KHz range. Such nozzles may or may not include a valve mechanism to control the rate of liquid flow. Valveless versions of such nozzles, as shown in U.S. Pat. Nos. 3,103,310; 3,121,534; and 3,214,101 to Lang, Watson, and Perron respectively, atomize a liquid in response to amplified vibrations of an orifice or opening at the discharge end of the nozzle; flow rate is controlled by other means. Such nozzles with valve mechanisms, as shown in U.S. Pat. Nos. 4,000,852 and 4,067,496 to Martin, additionally control the flow rate of a fuel with a valving member which opens and closes the orifice in response to the amplified vibrations.
Further, it is well-known in the prior art that such nozzles should be vibrationally insulated to reduce or minimize energy losses from the vibrating nozzle to its mounting or interface with nonvibrating means. Lang and Perron in the above mentioned patents disclose chuck-type mounts having three rigid, circumferentially arrayed, centering screws which embrace or hold the nozzles in so-called nodal planes, i.e., nonvibrating planes oriented normal to the longitudinal axes of the nozzles. The screws in the Perron chuck loosely embrace the nozzle to allow radial vibration of the nozzle due to or in accordance with Poissons ratio. Martin et al, in additional U.S. Pat. Nos. 4,052,004 and 4,251,031, teaches that it is difficult in practice to accurately determine vibrational nodes of such nozzles. The Martin et al patents disclose the use of resilient mounts (rubber O-rings) supporting the body portions of the nozzles in protective housings. The resilient mounts embrace the nozzles close to nodal planes normal to the longitudinal axes of the nozzles and yield in response to both longitudinal and radial vibrations, thereby avoiding or reducing the need to accurately determine vibrational nodes.
The Martin et al patent '031 further discloses the feature of dispensing with a metal fuel inlet tube rigidly connected at one end directly to the nozzle and connected at the other end to a somewhat flexible tube on the outside of the housing. While the particular structural arrangement disclosed in the '031 patent may have certain disadvantages, the basic concept of dispensing with the metal inlet tube extending out of the protective housing is advantageous with respect to structural damage vulnerability of the tube and with respect to inherent energy losses to the somewhat flexible tube, particularly wide variations in energy losses due to inadvertent misalignment of the rigid and somewhat flexible tube during factory installation or during field maintenance. Inadvertent misalignment not only affects energy losses but further causes wide variations in the amount of fuel metered by each nozzle for a given electrical energy input to the piezoelectric crystal.